The present invention relates to a radio communication system and a radio monitoring control system.
Attention is being focused on a concept of Internet of Things (IoT) that collects signals related to the state of various devices via Internet and distributes signals controlling many devices based on the content of collected signals to implement highly efficient operation of various systems including many devices as components. Development of various techniques is underway toward implementation of the IoT earnestly.
To implement the IoT, a sensor which monitors information of the device and an actuator which controls operation of the device needs to be coupled with the Internet. Since a plurality of devices constituting a system include many sensors and actuators, coupling by radio communication which eliminates the need of cables as a physical coupling means is preferable from the viewpoint that restraints to the operation status of devices is solved and installation costs of the hardware related to the coupling may be reduced.
Power of the electromagnetic wave is transmitted using a polarized wave generated in a direction at the right angle to the propagation direction. Thus, when many sensors and actuators are fixedly installed on many devices, the electromagnetic wave transmitted by radio reaches an access point of the Internet in the state polarized in various directions.
On the other hand, it is difficult to increase the transmission power of the sensor and the actuator due to restraints of the power consumption in the radio circuit. Thus, deterioration of the communication quality caused by a difference between a reaching polarized wave and a polarized wave suitable for reception may become significant.
For the electromagnetic wave, Japanese Patent Application Publication No. Hei 6-311135 discloses a configuration where a receiver receives two polarization components orthogonal to synthetic waves of a plurality of electromagnetic waves simultaneously and individually using two antennas which are spatially orthogonal to each other, and synthesizes two reception signals thus obtained to maximize the reception signal intensity and thereby improve the signal to noise ratio of the reception signal.